1. Field of the Invention
The present invention relates to a device and a method for testing a solar panel, and more particularly, to a sound wave testing device and a method for testing a solar panel.
2. Descriptions of the Related Art
Various defects may be generated during the manufacturing process of solar panels, for example, diffusion of silicon materials, passivation, cracks, and pollutants, sintering defects or the like. These defects not only reduce the conversion efficiency of the solar panels, but also cause potential risks with future use. Therefore, the inspection of the defects becomes very important for the quality control of the solar panels. Currently, the inspection of the defects of solar panels mainly relies on visual inspection. However, visual inspection is only able to only detect gross cracks but is unable to detect other types of defects such as fine cracks.
Subsequent damage can be avoided if solar panels with such fine cracks can be detected and discarded as early as possible in the manufacturing process. Fine cracks, though they won't initially cause a fracture in the solar panels, they might gradually enlarge during subsequent manufacturing procedures when the solar panels are usually exposed to high mechanical loads, thus causing a fracture in the solar panels. Therefore, discarding the solar panels with fine cracks during the initial stage of the manufacturing process will help to improve the economic effectiveness of the subsequent manufacturing process.
A lot of methods for identifying fine cracks in solar panels have been proposed in the prior art, for example, the manual testing method and methods using ultrasonic waves or infrared rays. According to the manual testing method, a solar panel is swung just like a fan, and if an abnormal sound is produced, the solar panel is defective. However, this manual testing method suffers from considerable errors because it is not supported by accurate data. When ultrasonic waves are used, mechanical stress may cause fractures in the solar panel. Furthermore, although using infrared rays can test for cracks in solar panels and elements more effectively, it tests for cracks by virtue of a temperature difference; hence, it will also fail in case of defects that will not present a temperature difference.
On the other hand, there is also a testing method that can effectively test for various defects of a solar panel through the electroluminescence (EL) of the solar panel. However, defects found by this testing method may also indicate an uneven thickness of the solar panel in addition to the existence of cracks, so it cannot be specially used for the testing of cracks. Moreover, as restricted by the optical lens, this testing method cannot capture the image of an object that is 2 meters wide from a distance of less than 1 meter; however, the transferred heights of solar panel production lines are generally no greater than 1.3 m and, are usually mostly around 1 meter. Therefore, to inspect the defects of the solar panels in the production lines, a plurality of cameras with high magnification factors must be used to capture images and then the images are combined together for inspection. Although this testing method is simple, the hardware cost thereof is disproportionally high due to the high price of infrared cameras with high magnification factors, and this has hindered the widespread use of this testing method.
Accordingly, an urgent need exists in the art to provide a testing device that is simple to operate, has a low hardware cost and can prevent damage to the solar panels during the testing process.